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Evaluating Emergency Strategies after Rabies Re-introduction

This study evaluates alternative strategies for controlling and eradicating rabies after its re-introduction in a naïve population. The simulation-based approach compares the effectiveness and feasibility of limited control areas, ring vaccination, and varying bait densities.

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Evaluating Emergency Strategies after Rabies Re-introduction

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  1. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion Scenario-analysis evaluating emergency strategies after rabies re-introduction Hans-Hermann Thulke & Dirk Eisinger Helmholtz Centre for Environmental Research UFZ :: Dept. of Ecological Modelling Leipzig/Germany Thomas Selhorst & Thomas Müller FLI Friedrich-Löffler-Institut :: Institute for Epidemiology Wusterhausen/Germany

  2. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion Scope: Rabies-free region + naïve population X Large scale countrywide vaccination successful in past • here economically useless Strategy: Limited control area

  3. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion X X X X X X X X X X X X X X Strategy: Limited control area Unvaccinated area Compact circle with 20 baits per km2 Vaccinated area X Increase Rabies detection control area… Target: Eradication + Avoiding breakout from control area

  4. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion 3 X X X X X X X X X X X X X X X X X X X X X X X X X X X X Alternative: Ring (Vaccinated area constant + number of baits equal + distance differs) CIRCLE RING X X CONTAIN COMBAT

  5. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion ? Simulation results: Circle vs. Ring (10.000 repetitions) RING CIRCLE Risk of Breakout Time [campaigns]

  6. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion Ring design: Strategy Risk of breakout higher   Public Health Economy Prolongation of measure (inner part vaccinated later) More cases of rabies (inner part epidemic starts)

  7. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion Compact control area around detection is mandatory! Eisinger et al. (2005) BMC Inf Dis 5:10 Emergency vaccination of rabies under limited resources – combating or containing?

  8. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Alternative: Bait density (Immediate combat + Number of baits equal + vaccinated area differs) DOUGH CIRCLE 20 baits per km2 40 baits per km2 10 baits per km2 COMBAT Focused COMBAT COVER

  9. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion Simulation results: Area vs. density ? (10.000 repetitions) Risk of Breakout [%] _ _ +  Dough thinner … Dough thicker 

  10. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion Dough design by: Strategy slightly thinner advantageous Public Health Economy The thicker the fewer rabies cases The thicker the quicker is eradication

  11. Conceptual frame – Alternative Ring – Alternative Dough – Conclusion X x Conclusion Model-based pre-testing helpful • Development and evaluation of alternatives Ring not applicable • Immediate combat of the outbreak is mandatory Lower bait density and larger area beneficial • Trading-off between success and control costs or rabies occurrence Need for further research! • Mixed application according to situation ?  

  12. Thank you

  13. Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook 5 Evaluation of relative performance of alternative scenarios  Simulation experiment Model Description

  14. Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook suscept. infected infectious empty Simulation model – Rule based Model realisation Population • Individual foxes (Position & age, sex & disease state) Seasonality • Reproduction in spring • Dispersal in autumn Spatial organization • Fox families in grid cells i.e. Sayers et al. 1985

  15. Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook Model rules :: Biology Individuals: Mortality Reproduction Bait uptake Subadults: Dispersal

  16. Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook Model rules :: Rabies transmission Neighborhood contacts

  17. Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook Model rules :: Rabies transmission Dispersal Neighborhood contacts Mating activity

  18. Scenario deduction – Model description – Scenario evaluation – Conclusion & outlook Model rules :: Bait distribution • 1 - 40 baits/km2 (Spring & Atumn campaigns) • Spatial assignment to fox families • Bait competition • Individual bait uptake

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